In one embodiment, this invention relates generally to a top drive system for a drilling rig.
Top drive is the oilfield definition of a power swivel in combination with certain additional features which facilitate torque reaction and pipe handling.
A power swivel is a hydraulic or electric powered rotating device which is suspended in or on the derrick, and which drives the drill pipe from above the rig floor, thus the name top drive. It replaces the rotary table, which drives the pipe from lower down, at the rig floor level.
The power swivel generates torque which is reacted by vertical track member(s) in the derrick in which the power swivel rides up and down. That is, this track is arranged such that the swivel torque is restrained no matter where the power swivel is vertically positioned in the derrick.
For lower torque levels, the vertical track members have historically been 1 or 2 wire ropes, tensioned between the top of the derrick and the rig floor. Torque reaction arm(s) mounted to the swivel are attached to the rope(s) by either common U-shaped fittings called shackles which slide up and down against the rope(s), or sheaves (pulleys) which provide rolling contact against the rope(s). This approach is low cost, fairly quick to rig up, and the loads imparted to the derrick by power swivels rated at lower torque levels are generally not significant. This is good for the rental tool business which rents the lower torque range of portable power swivels and cannot afford to be concerned with generating stresses in the customer""s derrick.
For torque levels in the higher ranges, some form of rigid steel track members have been used, either attached to the derrick from top to bottom, or attached only at the top and bottom. In either of these cases, significant loads resulting from the swivel torque are transmitted to the derrick, and the derrick stress levels must be examined for safety.
The portable rental tool industry needs top drives which can be installed in any derrick without adding any torque loading whatsoever.
It is an object of this invention to provide a top drive system which can be installed in any derrick without adding any torque loading whatsoever.
It is a further object of this invention to provide a device which permits measurement of the torque being generated by the top drive.
It is another object of this invention to provide a top drive system which accomplishes multiple purposes, including torque reaction, torque measurement, and pipe handling, in a simple and low cost system.
In one embodiment, the invention provides an arrangement of a torque absorber unit, a track unit, a carriage unit, a power swivel, and linkage arms, for use on a drilling rig comprising a drilling rig floor structure and a mast structure positioned on the drilling rig floor structure.
For brevity, the arrangement is described in its installed configuration. The track unit comprises a track having an upper end and a lower end and a longitudinal axis. The track is mounted in the mast structure and to the drilling rig floor structure in a manner which permits limited rotational movement around the longitudinal axis of the track. The torque absorber unit is connected to the lower end of the track unit and to the drilling rig floor structure and limits rotation of the track. The carriage unit is mounted for vertical travel on the track and is capable of exerting torque to the track around the longitudinal axis of the track. The power swivel is for rotating the drill pipe and is suspended in the mast structure. At least one pair of linkage arms extends from opposite sides of the power swivel to opposite sides of the carriage unit. The linkage arms are mounted to both the power swivel and the carriage unit for pivoting movement in a horizontal plane. Torque generated by the power swivel can be transmitted from the power swivel to the drilling rig floor structure via the at least one pair of linkage arms, the carriage unit, the track unit and the torque absorber unit.
In another embodiment of the invention, there is provided a method for absorbing torque generated by power swivel in a drilling rig. The method is preferably carried out using the above described apparatus. The method is carried out by rotating a drill pipe with the power swivel, which results in the generation of reaction torque. The reaction torque is transmitted from the power swivel to the drilling rig floor structure via the at least one pair of linkage arms, the carriage unit, the track unit and the torque absorber unit.
In a preferred embodiment, the torque output from the power swivel is further measured. This is easily accomplished where the torque absorber unit is the form of a hydraulic cylinder coupled to a pressure gauge which has been calibrated to measure torque output from the power swivel.
In a further embodiment of the invention, there is provided a method for rotationally manipulating, with respect to a vertical axis, a power swivel in a drilling rig. The method is preferably carried out in the above described apparatus in an embodiment wherein the torque absorber unit comprises a hydraulic cylinder and piston mechanically connected at one end to the track and at the other end to the drilling rig floor structure. The apparatus further comprises a hydraulic actuator means in operable association with the torque absorber unit for selectively positioning the piston in a desired position. The hydraulic actuator means, preferably a pump and control valve, is employed to position the piston in a desired location, which in turn manipulates the rotational orientation of the power swivel via the track unit, the carriage unit, and the at least one pair of linkage arms. Thus, the same hydraulic cylinder that is used for torque reaction and torque measurement can be used for torque track manipulation as well. By providing pipe handling means facing outwardly from the power swivel, the same hydraulic cylinder can be further employed to perform top drive pipe handling functions.
The invention thus provides a drilling rig with top drive functions using a simple, low cost machine.